644456343221 has 2 divisors, whose sum is σ = 644456343222. Its totient is φ = 644456343220.

The previous prime is 644456343149. The next prime is 644456343229. The reversal of 644456343221 is 122343654446.

It is a happy number.

644456343221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 356635896100 + 287820447121 = 597190^2 + 536489^2 .

It is a cyclic number.

It is not a de Polignac number, because 644456343221 - 2³⁴ = 627276474037 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644456343229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322228171610 + 322228171611.

It is an arithmetic number, because the mean of its divisors is an integer number (322228171611).

Almost surely, 2^644456343221 is an apocalyptic number.

It is an amenable number.

644456343221 is a deficient number, since it is larger than the sum of its proper divisors (1).

644456343221 is an equidigital number, since it uses as much as digits as its factorization.

644456343221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1658880, while the sum is 44.

Adding to 644456343221 its reverse (122343654446), we get a palindrome (766799997667).

The spelling of 644456343221 in words is "six hundred forty-four billion, four hundred fifty-six million, three hundred forty-three thousand, two hundred twenty-one".